The present invention relates to an improved valve bridge assembly and methods of manufacturing or rebuilding such assemblies.
In larger, internal combuston engines, for example, diesel engines used in locomotives, a valve bridge is part of the mechanism utilized to actuate the two exhaust valves that are associated with an engine cylinder. Typically, each valve bridge includes a main body portion and a cross-arm portion having outer, distal ends cooperative with the valve stems of the two associated exhaust valves. The rocker arm assembly of the engine periodically causes the valve bridge, and thus the exhaust valves, to be moved in a direction parallel to the longitudinal axes of the exhaust valves so as to open the valves.
Lash adjusters have long been used with valve bridges to improve the operation of the exhaust valves and, thus, the overall operation of the engine. Toward this end, a lash adjuster socket is formed in each of the outer, distal ends of the cross-arm portion of a valve bridge, and a lash adjuster is press-fit within each of these sockets. The lash adjusters are positioned so that they are in direct contact with the upper ends of the valve stems. The use of lash adjusters minimizes clearance problems in the exhaust valve actuating mechanism and compensates for thermal expansion and wear in this mechanism. The lash adjusters also serve to automatically adjust the exhaust valve actuating mechanism for smooth, efficient operation and to reduce maintenance of the associated parts of that mechanism.
It has long been an accepted practice in the industry to rebuild the valve bridges in an engine as part of a regular engine maintenance program. The rebuilding of a valve bridge generally includes the replacement of the lash adjusters (originally press-fit into the valve bridge) with either new or "remanufactured," press-fit type lash adjusters. However, after such a conventional valve bridge has been rebuilt two or three times, it has frequently been found that one or both of the lash adjuster sockets have become so oversized, out-of-round, etc., due to wear that standard size, new or re-manufactured, press-fit type lash adjusters can no longer be press-fit within the sockets. Insofar as the industry has been concerned, valve bridges that have such worn lash adjuster sockets are no longer considered as being usable, and it has been the general practice in the industry to discard or scrap such worn valve bridges.
There are approximately eighteen million valve bridges in use at the present time. One major company in the industry discarded over two hundred thousand worn valve bridges in the last several years and another company has over one hundred and fifty thousand worn valve bridges now awaiting scrapping. Since the cost of a new valve bridge is presently over forty-five dollars, the industry practice of discarding or scrapping worn valve bridges is one of considerable economic significance.
Accordingly, the industry has for years been attempting to solve the problem of how to avoid discarding or scrapping these worn valve bridges when, in effect, most of these worn valve bridges would still have a long, useful life, if it were not for the fact that their lash adjuster sockets had become worn and oversized. In this regard, some worn valve bridges are repaired by "filling" the worn lash adjuster socket with a weldment and then reaming or grinding out the socket to its original, inner diameter dimension. Although this method of rebuilding worn valve bridges generally produces satisfactory results, it is a time consuming procedure and thus is relatively expensive.
Another proposed solution to this longstanding problem contemplates that the outer distal ends of the cross-arm portion of the valve bridges be swadged through the use of a press in order to reduce the inner diameter dimension of a worn lash adjuster socket, thereby enabling a standard size, press-fit type lash adjuster to be press-fit within the socket again. The difficulty with this proposal is that there is a tendency for the cross-arm portions of the worn valve bridges to crack as a result of this swadging action. In addition, it is difficult to ascertain the amount of swadging that can be accomplished without cracking the cross-arm portion of the valve bridge.
Still others in the industry have proposed to solve this longstanding problem by dipping worn valve bridges in chrome plating solutions in order to plate the valve bridges, including the inside of their lash adjuster sockets. The sockets are then reground to their original inner dimension so that standard size, press-fit type lash adjusters can be press-fitted therein. This proposal, however, has not been widely adopted by the industry because particles of the plating frequently "flake off" and get into the hydraulic oil used with the lash adjusters thereby tending to cause the lash adjusters to "freeze."
It has also been suggested as a solution that the inside surfaces of a worn lash adjuster socket be knurled so that the socket can again accept a standard size new or remanufactured lash adjuster. Knurling has also not found acceptance in the industry because of the expense involved and because it does not really provide a satisfactory rebuilt valve bridge.
In summary then, the industry has, for many years, followed the practice of discarding or scrapping used valve bridges which were structurally sound except for the fact that one or both of their lash adjuster sockets had become oversized, out-of-round, etc. This practice has prevailed even though the industry has long recognized that this practice presents a serious economic problem with respect to minimizing the cost of maintaining and repairing internal combustion engines.
Although a variety of solutions to this longstanding problem has been proposed, none of the proposed solutions has received widespread acceptance in the industry. Consequently, large numbers of worn valve bridges utilizing press-fitted adjusters are still being discarded or scrapped each year, even though, as above-noted, these valve bridges would be perfectly capable of continued usage in engines were it not for the fact that one or both of their lash adjuster sockets had become worn oversized to such a degree that the bridges are unusable.
My improved valve bridge assembly and methods of manufacturing the same, both new and rebuilt, provide a novel, inexpensive, and practical solution to this problem which has faced the industry for many, many years. More specifically, my improved valve bridge includes a cross-arm with distal ends and lash adjuster sockets adjacent to each of the distal ends. The lash adjuster sockets, when new, have standard sized openings which receive standard sized lash adjusters, each of which have a body with a flange, an upper cylindrical portion, and a radially projecting rib member adjacent to and above the flange. The rib member extends around the circumference of the upper cylindrical portion and has an outer diameter dimension greater than the mean diameter dimension of the standard sized opening in the socket when new.
My improved method of manufacturing my improved valve bridge assembly disclosed herein has two alternative embodiments. The first is used to rebuild a worn valve bridge having unthreaded lash adjusters and includes the steps of removing the used, old valve adjusters from the valve bridge, cleaning the bridge, measuring or in some other manner ascertaining the dimensions of the worn lash adjuster sockets in the valve bridge, selecting a specially made new or remanufactured unthreaded lash adjuster whose outer body dimensions are comparable to the inner diameter dimension of the worn lash adjuster sockets, and then press-fitting the selected oversized lash adjuster into the worn lash adjuster socket of the valve bridge.
The performance of my improved method can be expeditiously accomplished by having available groups of oversized unthreaded lash adjusters, with the adjusters in each of the groups being oversized by a specific, predetermined amount. For example, one group would be oversized by fifteen thousandths of an inch, the second by thirty thousandths of an inch and the third by forty-five thousandths of an inch over the standard diameter of a lash adjuster. Thus, for example, a person rebuilding worn valve bridges need only measure an inner diameter dimension of a worn lash adjuster socket and then readily select an oversized lash adjuster from the group of lash adjusters having an oversized dimension comparable to the measured inner diameter dimension of the worn socket.
To enable a person using my improved method to quickly select the compatible oversized lash adjuster, color coding can be applied to the oversized lash adjusters. The color coding will indicate the amount that a particular lash adjuster is oversized with respect to the dimension of the standard size lash adjuster.
My improved method described above works well to solve the problem of rebuilding worn valve bridges that have been manufactured to accept press-fitted lash adjusters. For valve bridges not already manufactured, however, an alternative embodiment of my improved method greatly increases the useful life of the original lash adjusters and greatly reduces the otherwise frequent need for rebuilding either the lash adjuster sockets or the lash adjusters themselves. This alternative embodiment method can also be used to remanufacture or rebuild worn valve bridges that were originally manufactured to accept press-fitted lash adjusters. This latter method includes the steps of threading an outer portion of the cylindrical body on the lash adjusters, threading an inner portion of the lash adjusters sockets so that the threaded portions of the lash adjusters can be screwed into, and mate with, the threaded portions on the sockets, and then screwing the lash adjusters into place with the sockets on the valve bridge.
The threaded lash adjuster-and-socket combination produced by this latter alternative method will continue to hold the lash adjusters in place in the sockets long after an unthreaded adjuster would have slid out of a worn, unthreaded adjuster socket. For example, I have found that a valve bridge originally manufactured with the threaded lash adjuster-and-socket combination has a useful life that is four to five times the useful life of the old, standard press-fit type of lash adjuster-and-socket combination. Even though the threaded socket of my improved valve bridge will eventually wear out with use, the threads in the socket and on the adjuster will continue to mate even as they become worn down--until they have worn down so far that they no longer mate sufficiently well to hold the adjuster within the socket.
For over twenty years, the industry has been well aware of the problem for which my apparatus provides a ready and practical solution. Yet prior to my invention, no one had a satisfactory solution to this problem, much less developed a product or method similar to my product and corresponding methods as described and claimed herein. In this regard, literally millions of used valve bridges have been discarded or scrapped over the years by those in the industry, even though, but for the fact that their lash adjuster sockets had become oversized, their used valve bridges were structurally sound and capable of many more years of satisfactory performance in internal combustion engines. An incentive for those in the industry to develop a solution to this longstanding problem has always existed since a new valve bridge costs over fourty-five dollars; whereas, a new lash adjuster costs under three dollars and a remanufactured lash adjuster costs even less. Furthermore, even though my invention has been available to the industry for only a few months, it has already been accepted and recognized by persons in the industry as being a practical answer to this longstanding problem and one that is significantly superior to the methods which have heretofore been proposed to overcome this problem.
It is therefore an object of my invention disclosed herein to provide an improved valve bridge and method of rebuilding a valve bridge wherein one or both of the lash adjuster sockets therein have become oversized, out-of-round, etc., due to wear.
It is another primary object of my present invention to provide a valve bridge assembly with a lash adjuster that compensates for wear of the lash adjuster socket and will thereby remain in position in a worn lash adjuster socket.
It is also an object of my present invention to provide an improved valve bridge assembly that has a rib member surrounding the circumference of the upper portion of the body of a lash adjuster and having an outer diameter dimension greater than the mean diameter dimension of the lash adjuster socket when new. The lash adjuster will thereby remain in position even as the lash adjuster socket becomes worn somewhat oversize through use.
A still further object of my present invention is to provide an improved valve bridge and method of rebuilding it wherein the improved method includes the steps of removing the old, used, unthreaded lash adjusters from the lash adjuster sockets in the valve bridge, cleaning the valve bridge, measuring an inner diameter dimension of each of the worn lash adjuster sockets, selecting new or remanufactured oversized, unthreaded lash adjusters having out diameter dimensions comparable to the inner diameter dimensions of the oversized lash adjuster sockets, and then reassembling the valve bridge by press fitting the oversized lash adjusters into the measured lash adjuster sockets.
An even further object of my present invention is to provide an improved valve bridge and method of rebuilding it wherein each oversized lash adjuster includes an indicia on its body indicating the size of its outer diameter dimension so as to facilitate the selection of the oversized lash adjuster having outer diameter dimensions comparable to the inner diameter dimensions of an oversized lash adjuster socket.
An additional object of the present invention is to provide an improved valve bridge and method of manufacturing or remanufacturing it wherein each lash adjuster and lash adjuster socket is at least partially threaded and the lash adjusters are screwed into place in the sockets. The lash adjusters will thereby remain in position within the sockets long after conventional, press-fit lash adjusters would have worn out of position in the sockets.
A yet additional object of my present invention is to provide an improved valve bridge and method of manufacturing wherein each lash adjuster has a flange with means for gripping or clamping the adjuster or screwing the adjuster into place in a lash adjuster socket.
These and other objects and advantages of my present invention will become apparent from the following description of the preferred embodiment of this invention, described in connection with the accompanying drawings.